Abstract: The paper discusses the thermal network analysis in thermal design of the spacecraft, dealing with the calculation of temperature field of first communication satellite of China, and gives the steady-state temperature of 250 nodes which are corrected. The computing results are compared with the data measured in ground simulation and the data telemetered from orbiting satellite. The results of comparison indicate that the computing deviations are mostly within 2～8℃. In addition, the author proposes few on the further thermal design.